A filter that attaches a prefix to every line of data read.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@271515 13f79535-47bb-0310-9956-ffa450edef68

proposal/sandbox/filterreaders/src/main/org/apache/tools/ant/filters/PrefixLines.java

@@ -0,0 +1,122 @@
+package org.apache.tools.ant.filters;
+
+import java.io.FilterReader;
+import java.io.IOException;
+import java.io.Reader;
+
+import org.apache.tools.ant.types.Parameter;
+import org.apache.tools.ant.types.Parameterizable;
+
+/**
+ * Attach a prefix to every line
+ *
+ * @author <a href="mailto:umagesh@apache.org">Magesh Umasankar</a>
+ */
+public final class PrefixLines
+    extends FilterReader
+    implements Parameterizable
+{
+    /**
+     * prefix key
+     */
+    private static final String PREFIX_KEY = "prefix";
+
+    private Parameter[] parameters;
+
+    private boolean initialized = false;
+
+    private String prefix = null;
+
+    private String queuedData = null;
+
+    /**
+     * Create a new filtered reader.
+     *
+     * @param in  a Reader object providing the underlying stream.
+     */
+    public PrefixLines(final Reader in) {
+        super(in);
+    }
+
+    public final int read() throws IOException {
+        if (!initialized) {
+            initialize();
+            initialized = true;
+        }
+
+        int ch = -1;
+
+        if (queuedData != null) {
+            if (queuedData.length() == 0) {
+                queuedData = null;
+            } else {
+                ch = queuedData.charAt(0);
+                queuedData = queuedData.substring(1);
+            }
+        } else {
+            ch = in.read();
+            while (ch != -1) {
+                if (queuedData == null) {
+                    if (prefix != null) {
+                        queuedData = prefix;
+                    } else {
+                        queuedData = "";
+                    }
+                }
+                queuedData += (char) ch;
+                if (ch == '\n') {
+                    break;
+                }
+                ch = in.read();
+            }
+            if (queuedData != null) {
+                return read();
+            }
+        }
+        return ch;
+    }
+
+    public final int read(final char cbuf[], final int off,
+                          final int len) throws IOException {
+        for (int i = 0; i < len; i++) {
+            final int ch = read();
+            if (ch == -1) {
+                if (i == 0) {
+                    return -1;
+                } else {
+                    return i;
+                }
+            }
+            cbuf[off + i] = (char) ch;
+        }
+        return len;
+    }
+
+    public final long skip(long n) throws IOException {
+        for (long i = 0; i < n; i++) {
+            if (in.read() == -1) {
+                return i;
+            }
+        }
+        return n;
+    }
+
+    /**
+     * Set Parameters
+     */
+    public final void setParameters(final Parameter[] parameters) {
+        this.parameters = parameters;
+        initialized = false;
+    }
+
+    private final void initialize() {
+        if (parameters != null) {
+            for (int i = 0; i < parameters.length; i++) {
+                if (PREFIX_KEY.equals(parameters[i].getName())) {
+                    prefix = parameters[i].getValue();
+                    break;
+                }
+            }
+        }
+    }
+}